1. Field of the Invention
The present invention pertains to a method for selecting a subterranean earth formation zone for receiving slurried solids wastes and the like and for injecting a predetermined quantity of said wastes in the selected zone.
2. Background
Certain types of waste material, including viscous liquids and slurries of particulate solids,-may be disposed of by injecting the material into a subterranean earth formation. Typically, in disposing of solids wastes, the solids are reduced to relatively fine particulates and a slurry is prepared, usually with water as the carrier liquid, which is suitable for injection into a selected zone of an earth formation through an injection well. Moreover, when a slurry of particulate solids is injected through a hydraulic fracture in the selected zone, the liquid portion of the slurry leaks off into permeable strata, leaving the solids as a deposit which grows thicker as exposure time increases. Some portions of the fracture may become completely plugged with the solids "filter cake" while other portions of the fracture may remain open to allow the slurry to flow generally laterally outwardly from the injection well and between the layers of filter cake.
My U.S. Pat. No. 5,226,749, issued Jul. 13, 1993 and assigned to the assignee of the present invention, discloses and claims a method for disposing of slurried solids wastes in a formation zone of interest which has plural layers of material which have different permeabilities to provide alternate layers of filter cake and channels adjacent the layers of formation of relatively low permeability which permits injection of a substantial amount of material. U.S. patent application Ser. No. 08/032,951, filed Mar. 17, 1993 and also assigned to the assignee of the present invention, pertains to a waste disposal method taking into consideration that a selected zone for disposal preferably is bounded above and below by zones which have higher in situ stresses and, preferably, low permeability so that the waste material is confined to the disposal zone and hydraulic fractures do not break out vertically into zones which are in communication with fresh water sources, for example.
However, other factors should be considered when selecting subterranean earth formation zones for disposal of waste material and for carrying out the waste disposal process. A reasonably accurate estimate of the volume of material which may be injected into a selected zone should be obtained so that proper preparation for the injection process is possible, that is with respect to the volume of slurry expected to be injected, and to provide assurance that the injected volume will not result in extension of one or more fractures outside of the disposal zone. To this end certain factors should be determined such as fluid leak-off behavior, flow behavior in the presence of filter cake on the fracture faces, an estimate of how closely multiple fractures, if expected to be present, tend to be positioned and whether or not the fracture is elastically deformed and/or the fracture faces are subject to inelastic compaction. It is to these ends that the present invention has been developed.